In accordance with the prior art, Message Usage Recording and Billing Accuracy (MURBA) Logic Terminal Units (LTUs) are installed in telephone company (TELCO) central offices. These LTUs provide access to TELCO central office lines to enable one way dial through billing accuracy testing of the public switched network under control of a centralized host computer. This arrangement enables the host computer to remotely generate and record test calls originating and terminating at offices where the logic terminals have been installed. Test call records are then compared with billing records to evaluate billing accuracy. Under the MURBA system, a centrally located host computer accesses LTUs that have been installed in selected central offices. The remote host computer then, via the LTU, simulates typical customer telephone calls over the public switched network. This procedure generates a control sample of originating calls representative of all calls generated for that office or area. All billing details of this control sample are recorded in the on-line database of the host computer. The host computer rates (calculates the billing of) the generated calls, and compares the results with records generated by the TELCO accounting system. Management summaries and discrepancy reports are then produced.
In order to transform the MURBA system from a billing verification system into a system which would verify the proper operation of the switched network, the following changes would be beneficial.
1. Positive identification of the termination point should take place when test calls ar made. The present MURBA system operates in the following way: When a prior art LTU receives a test call it responds wit a single tone to the originating LTU. Therefore, the originating LTU only verifies that another LTU was reached, not whether a particular LTU was reached.
2. It would b beneficial for a test system to employ devices that were inexpensive enough to be deployed ubiquitously throughout the network, enabling complex, real-time testing of any combination of network origination and termination points.
3. The originating LTU should dependably control and monitor the duration of the test call. The prior art system simply transmits a signal to the terminating LTU, which sends a signal back to the originating LTU. If other types of signals are received at the originating LTU, the are sometimes mistaken for the return signal of a far-end LTU (such as when a component frequency of a foreign signal matches the LTU signal frequency). Therefore, the timing function of the billing process cannot be consistently validated by the use of LTUs.
4. A network verification system should be able to test terminating access billing. Since the originating end of a test call disconnects before the terminating end of a test call, the prior art MURBA system cannot detect when the terminating end disconnects. In today's telecommunications environment, one TELCO may originate a call, an Interexchange Carrier (IEC) may transport the call over long distances, and a second TELCO may terminate the call. The first TELCO bills the IEC for the origination of the call, and the second TELCO bills the IEC for the termination of the call. IECs are therefore interested in verifying when the terminating end disconnects, in order to verify that the billing from the terminating TELCO is correct. The MURBA system utilizes standard 103 Type data sets in each LTU. The far end data set periodically monitors for an incoming signal. If consecutive monitoring cycles show that no signal is present, the LTU disconnects. Because of this process, the near end LTU (and therefore the centralized host computer) cannot determine when the far end LTU actually disconnects. The termination billing therefore cannot be accurately verified by using the prior art MURBA system.
5. A network verification system should be capable of testing non-billed calls (e.g., local calls and operator assisted calls). This is not presently done because toll records would not be produced for these calls by the TELCO Accounting Department for later comparison with MURBA results.
6. A network verification system should be able to test switch routines and translation functions following a switch cutover (placement of a new or replacement switching machine in the network). Tests should be performed to verify that the new switch can correctly direct calls to other switches or access points in the network, or verify that other switches and access points have been properly modified to direct calls to the new switch, on a real-time basis. If prior art LTUs were placed at every switching machine in the TELCO network, automated test calls could be made to and from the new switch, but the results of the test would have to await the receipt of the billing records (which would not include non-billed calls) in order to determine that the calls were properly routed.
7. An enhanced system should be able to handle Touch Tones, as well as dial pulses, both for call set-up and testing. The use of Touch Tones would allow direct access to the system from Touch Tone phones, prevent the misinterpretation of return signals, and allow for complex signaling between LTUs.
8. It would be beneficial for the enhanced system to perform diagnostics on the transmission quality of the network simultaneous to its other test capabilities.
9. Finally, it would be beneficial for a network verification system to begin timing from any pre-selected dialed digit. Since some switching machines begin sending calls to the next switching machine after receiving a pre-selected number of dialed digits (for example, some switches begin outgoing call set-up after the third dialed digit), small errors in billing could go undetected by using the MURBA system, which begins timing after all digits are dialed. IECs are particularly interested in those seemingly small amounts of time when repeated on millions of calls.
Accordingly, there exists a need for devices and methods for positively identifying the far-end test device, economically and ubiquitously placing test devices throughout the TELCO network, accurately controlling and monitoring the timing of test calls, testing of transmission characteristics of the network, and verification of the call completion capabilities of the network, including non-billed calls.